The Five Senses and Beyond: The Encyclopedia of Perception - Jennifer L. Hellier 2017

Retinopathy

Retinopathy or diabetic retinopathy is an eye condition that develops in individuals that have either Type 1 or Type 2 diabetes. This condition occurs when the blood vessels from the light-sensitive tissue at the retina are damaged. The blood vessels in the eye provide the necessary nutrients to the retina so that when light hits the eye, the retina processes the light rays into electrical impulses to travel to the visual cortex. The brain then converts these impulses into images with depth and distance. Diabetes is normally associated with complications of the body’s ability to properly store and utilize sugar. Increased levels of sugar affect the circulatory system of the retina or glucose that eventually causes damage to the blood vessels. According to the Centers for Disease Control and Prevention, millions of Americans ages 40 years and older have retinopathy due to either Type 1 or Type 2 diabetes. Americans who are 20 years and older are also at high risk, especially due to the correlation of increasing obesity rates in this age group within the United States. Women who have diabetes and are also pregnant have a greater rate of developing retinopathy.

Symptoms

With prolonged diabetes, retinal blood vessels start to leak fluid that distorts the curve of the lens in the eyes. This leads to blurry vision, spots, or floaters in the center or field of vision, and difficulty with night vision. Sudden loss of vision in one eye and seeing rings or flashing lights are also attributed to diabetic retinopathy. Risk factors for developing these symptoms include poorly controlled diabetes, poorly controlled blood pressure, high cholesterol levels, and sleep apnea. Macular edema is one prominent change to the eye in which there is swelling or thickening of the macula due to leaking fluid. Macular ischemia can also occur and is due to capillaries collapsing, causing blurry vision. There are several stages to diabetic retinopathy, including mild nonproliferative, moderate nonproliferative, severe nonproliferative, and proliferative retinopathy.

Stages

There are two main stages of diabetic retinopathy: nonproliferative retinopathy, in which the blood vessels start to leak fluid; and proliferative retinopathy, a later stage of the condition in which new blood vessels grow around the retina and the vitreous humor. Without treatment, the blood vessels might burst, resulting in cloudy sight or scars on the retina. In the beginning stages of this condition, swelling in blood vessels (microaneurysms) can occur. In moderate nonproliferative retinopathy, some of the blood vessels are blocked, causing the progression to severe nonproliferative retinopathy as more blood vessels are blocked. During proliferative retinopathy, new but fragile blood vessels are stimulated to grow in order to provide nourishment to the retina. When these new blood vessels pop due to their fragility, the released blood can lead to vision loss and blindness. In the later stages of the condition, leaks in the blood vessels can alter the eye’s jelly-like vitreous humor (located in the vitreous body between the lens and retina) and cause blindness.

Diagnosis and Treatment

Doctors can examine the state of the condition using a test called fluorescein angiography. A dye is injected through the veins and as the blood flows, the dye appears in the retina. Photographs of the retina are then evaluated to detect the progression of the disease. Individuals with diabetes can monitor the rate at which this condition progresses by adjusting their blood glucose intake and lowering their risk by controlling levels of blood sugar, blood pressure, and blood cholesterol to decrease the progression. If untreated, the scars on the back of the retina can pull the retina away from the back of the eye, leading to retinal detachment and resulting in permanent blindness. There are several options to treat the condition as shown in the accompanying table.

Simi Abraham

See also: Blindness; Retina; Visual System

Further Reading

Chee Wai Wong, Tien Yin Wong, Ching-Yu Cheng, & Charumathi Sabanayagam. (2014). Kidney and eye diseases: Common risk factors, etiological mechanisms, and pathways. Kidney International, 85, 1290—1302.

National Eye Institute. (2015). Facts about diabetic eye disease. Retrieved from https://nei.nih.gov/health/diabetic/retinopathy